1. Field of the Invention
The present invention relates to a method for early detection of abnormal tissue in a living body, and in particular to a method for manipulating temperature data obtained by the scanning of predetermined parts of the body so as to produce an objective indication of the probability of abnormal tissue.
2. Prior Art
Breast cancer is the most common cancer among women in the United States. Medical data based upon the size and shape of breast tumors at the time of surgery indicate that a marked improvement in the survival rate after surgery is most likely to come through early detection of the cancer; i.e., when it is small and asymptomatic. Thus, a great need has arisen for techniques and equipment that would aid in the early detection of cancerous or diseased tissue in the body. Extensive activity has been undertaken and devoted to development of methods and production of equipment useful in solving this problem. Although some of these methods and equipment may be functionally successful, actual utilization in practical clinical application has been thwarted due to health hazards, complexity, and/or the high cost of trained personnel and equipment.
At present, there are four recognized methods used in the diagnosis of breast cancer prior to biopsy. These are (i) physical examination; (ii) mammography; (iii) ultrasonography; and (iv) thermography. Mammography, which utilizes x-ray radiation, has been used extensively in the past. However, much controversy has arisen in recent years concerning excessive exposure to radiation in the detection of breast cancer. Consequently, many women now are unwilling to submit to necessary mammographic examinations which could save their lives.
Alternative techniques such as ultrasonography and thermography, which do not utilize ionizing radiation, have been developed and enhanced in recent years. Ultrasonography essentially "maps" sonar reflections and thermography "maps" infrared emissions from breast tissue respectively. In ultrasonography, the sound reflections are used to create a sonogram which can reveal alterations in the structure of normal breast tissue. Thermography is based upon the physiological observation that cancerous or otherwise diseased tissue, due to changes in vascular and metabolic activity, radiate more heat than normal, thereby elevating the temperature of the skin covering such tissue. Thus, it has been recognized that the higher skin temperature of diseased tissues can serve as a valid indicator of such a condition.
In conventional thermography, a specialized camera is used to expose a film with infrared emissions from selected surface portions of the body. The result is a thermal photograph showing temperature variations of the parts of the body scanned as bright and dark spots. Another thermographic technique known in the art is "contact" thermography, such as manufactured by Thermal Imagery, Inc., which is applied directly to the breasts and produces colored pictures. The so-called "Flexitherm" liquid crystal detection system is virtually a brassiere with cholesterol crystals that show heat changes. U.S. Pat. No. 4,055,166 to Simpson et al discloses a brassiere which includes a number of skin temperature sensors connected to battery powered integrated circuits, including storage registers for recording the sensed temperature data.
A distinct disadvantage to both ultrasonography and conventional thermography is that each depends upon a subjective analysis of the sonogram and thermogram, as the case may be, by a highly trained person. This results in reduced reliability and greater cost, making these techniques unacceptable for mass screening. The subjective nature of the analysis required by these techniques relates both to the determination of what the test results are, and to what they mean as well. For example, knowledge of the normal vascular patterns of the breast is a prerequisite to interpretation of thermograms, and there can be great variation in readings by different individuals and even in repeat interpretations of the same record by the same individual.
Schwamm of West Germany developed a system of thermography using an infrared probe (a Thermophil M202). He coupled his readings with a stress test, first using Novacaine injections or topical applications, and later substituting ice water. His rationale for such procedure is that the temperature of any part of the body is controlled by a thermal regulatory mechanism which responds to any type of body stress by vasoconstriction, with a subsequent reduction in the local temperature. The cardiovascular mechanisms which influence skin temperature of the hand, feet and other parts of the body are regulated by the sympathetic sector of the autonomic nervous sytem. Activation of the sympathetic processes results in the constriction of the blood vessels, reduction in their diameter, and a consequential decrease in peripheral circulation and skin temperature. Abnormal areas, such as those involved by cancer, do not manifest this same temperature reduction, because the blood vessels in the tumor do not constrict to the same degree as normal tissue under the same stimulation.
The present invention is an improvement on the work done by Schwamm, utilizing a direct infrared sensing device for gathering temperature data and an empirically developed methodology for manipulating such data so as to reliably detect the presence and location of diseased breast tissue.